Processing of non-ASCII usernames and passwords requires the SASLprep
implementation in LibIDN (http://www.gnu.org/software/libidn/).
This is needed for full conformance with the latest SASL protocol
drafts, but is optional in the library for improved portability.

Libgcrypt

The GNU SASL library ships with its own cryptographic implementation,
but it can use the one in libgcrypt (http://www.gnupg.org/)
instead, if it is available. This is typically useful for desktop
machines which have libgcrypt installed.

The command-line interface to GNU SASL requires a POSIX or Windows
platform for network connectivity. The command-line tool can make use
of GnuTLS (http://www.gnutls.org/) to support the STARTTLS modes
of IMAP and SMTP, but GnuTLS is not required.

Note that the library does not need a POSIX platform or network
connectivity.